The present disclosure relates generally to a shift register, and more specifically, to a shift register with opposite shift data and shift clock directions.
Shift registers, also known as shift rings, scan rings, or scan registers, are used as elements for moving digital data serially though digital semiconductor chips. Sequential logic latches in semiconductor chip designs are connected as part of some chip pervasive shift register. In many cases, shift rings are a form of serial communication and test access to semiconductor chips. These shift registers are connected to a grid clock or clock tree that is pervasively wired across large sections of the chip due to the need for shift register designs to operate synchronously.
Because current shift register designs operate synchronously across large sections of a semiconductor chip, their clocks are often connected to the existing functional clock grids or clock trees through shift register clock drivers. Since most chip pervasive shift registers are only used for chip initialization, servicing, and test access, the capacitive and resistive clock loads of these many shift register clock drivers connected to the functional clock grids are always burning power, non-productively, during the functional operation of the semiconductor chip because these shift registers are usually not in use.